Method and Apparatus for Removing Contamination from Substrate

ABSTRACT

A cleaning material is disposed over a substrate. The cleaning material includes solid components dispersed within a liquid medium. A force is applied to the solid components within the liquid medium to bring the solid components within proximity to contaminants present on the substrate. The force applied to the solid components can be exerted by an immiscible component within the liquid medium. When the solid components are brought within sufficient proximity to the contaminants, an interaction is established between the solid components and the contaminants. Then, the solid components are moved away from the substrate such that the contaminants having interacted with the solid components are removed from the substrate.

CLAIM OF PRIORITY

This application is a divisional application of U.S. patent applicationSer. No. 11/336,215, filed on Jan. 20, 2006, which claims the benefit ofU.S. Provisional Application No. 60/755,377, filed Dec. 30, 2005, andwhich is a continuation-in-part of U.S. patent application Ser. No.10/608,871, filed Jun. 27, 2003. The disclosure of each of theabove-identified patent applications is incorporated herein by referencein its entirety.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No.10/816,337, filed on Mar. 31, 2004, and entitled “Apparatuses andMethods for Cleaning a Substrate,” and U.S. patent application Ser. No.11/173,132, filed on Jun. 30, 2005, and entitled “System and Method forProducing Bubble Free Liquids for Nanometer Scale SemiconductorProcessing,” and U.S. patent application Ser. No. 11/153,957, filed onJun. 15, 2005, and entitled “Method and Apparatus for Cleaning aSubstrate Using Non-Newtonian Fluids,” and U.S. patent application Ser.No. 11/154,129, filed on Jun. 15, 2005, and entitled “Method andApparatus for Transporting a Substrate Using Non-Newtonian Fluid,” andU.S. patent application Ser. No. 11/174,080, filed on Jun. 30, 2005, andentitled “Method for Removing Material from Semiconductor Wafer andApparatus for Performing the Same,” and U.S. patent application Ser. No.10/746,114, filed on Dec. 23, 2003, and entitled “Method and Apparatusfor Cleaning Semiconductor Wafers using Compressed and/or PressurizedFoams, Bubbles, and/or Liquids.” The disclosure of each of theabove-identified related applications is incorporated herein byreference.

BACKGROUND

In the fabrication of semiconductor devices such as integrated circuits,memory cells, and the like, a series of manufacturing operations areperformed to define features on semiconductor wafers (“wafers”). Thewafers include integrated circuit devices in the form of multi-levelstructures defined on a silicon substrate. At a substrate level,transistor devices with diffusion regions are formed. In subsequentlevels, interconnect metallization lines are patterned and electricallyconnected to the transistor devices to define a desired integratedcircuit device. Also, patterned conductive layers are insulated fromother conductive layers by dielectric materials.

During the series of manufacturing operations, the wafer surface isexposed to various types of contaminants. Essentially any materialpresent in a manufacturing operation is a potential source ofcontamination. For example, sources of contamination may include processgases, chemicals, deposition materials, and liquids, among others. Thevarious contaminants may deposit on the wafer surface in particulate foiiii. If the particulate contamination is not removed, the devices withinthe vicinity of the contamination will likely be inoperable. Thus, it isnecessary to clean contamination from the wafer surface in asubstantially complete manner without damaging the features defined onthe wafer. However, the size of particulate contamination is often onthe order of the critical dimension size of features fabricated on thewafer. Removal of such small particulate contamination without adverselyaffecting the features on the wafer can be quite difficult.

Conventional wafer cleaning methods have relied heavily on mechanicalforce to remove particulate contamination from the wafer surface. Asfeature sizes continue to decrease and become more fragile, theprobability of feature damage due to application of mechanical force tothe wafer surface increases. For example, features having high aspectratios are vulnerable to toppling or breaking when impacted by asufficient mechanical force. To further complicate the cleaning problem,the move toward reduced feature sizes also causes a reduction in size ofparticulate contamination. Particulate contamination of sufficientlysmall size can find its way into difficult to reach areas on the wafersurface, such as in a trench surrounded by high aspect ratio features.Thus, efficient and non-damaging removal of contaminants during modernsemiconductor fabrication represents a continuing challenge to be met bycontinuing advances in wafer cleaning technology.

SUMMARY

In one embodiment, a method is disclosed for removing contamination froma substrate. The method includes an operation for disposing a cleaningmaterial over a substrate. The cleaning material includes a number ofsolid components dispersed within a liquid medium. The method alsoincludes an operation for applying a force to a solid component to bringthe solid component within proximity to a contaminant present on thesubstrate, such that an interaction is established between the solidcomponent and the contaminant. The method further includes an operationfor moving the solid component away from the substrate, such that thecontaminant that interacted with the solid component is removed from thesubstrate.

In another embodiment, an apparatus for removing contamination from asubstrate is disclosed. The apparatus includes a channel for receiving asubstrate. The channel is defined to include a constraining surfacepositioned in an opposing and substantially parallel orientation withrespect to a surface of the substrate from which contamination is to beremoved. The apparatus also includes a cleaning material disposed withinthe channel such that the substrate to be received by the channel issubmerged within the cleaning material. The cleaning material is definedas a liquid medium including dispersed solid components. The apparatusfurther includes an immiscible component generator disposed within thechannel to generate immiscible components within the cleaning material.The immiscible components are generated within the cleaning materialsuch that a motive force is applied to move the immiscible componentsbetween the constraining surface of the channel and the surface of thesubstrate from which contamination is to be removed.

In another embodiment, a method is disclosed for removing contaminationfrom a substrate. The method includes an operation for submerging asubstrate in a cleaning material such that a surface of the substratefrom which contamination is to be removed is positioned in an opposingand substantially parallel orientation with respect to a constrainingsurface. The cleaning material is defined to include solid componentsdispersed within a liquid medium. The method also includes an operationfor tilting the substrate together with the constraining surfacerelative to a horizontal plane. The method further includes an operationfor generating immiscible components within the cleaning material at alocation corresponding to an elevation lower than the substrate. Abuoyant force acting upon the immiscible components causes theimmiscible components to move over the substrate and between theconstraining surface and the substrate. Movement of the immisciblecomponents over the substrate causes a force to be applied to the solidcomponents within the liquid medium, such that the solid componentsinteract with contaminants present on the substrate.

Other aspects and advantages of the invention will become more apparentfrom the following detailed description, taken in conjunction with theaccompanying drawings, illustrating by way of example the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration showing a physical diagram of a cleaningmaterial for removing contamination from a semiconductor wafer, inaccordance with one embodiment of the present invention;

FIGS. 2A-2B are illustrations showing how the cleaning materialfunctions to remove the contaminant from the wafer, in accordance withone embodiment of the present invention;

FIG. 3 is an illustration showing a flowchart of a method for removingcontamination from a substrate, in accordance with one embodiment of thepresent invention;

FIG. 4A is an illustration showing an apparatus for removingcontamination from a wafer, in accordance with one embodiment of thepresent invention;

FIG. 4B is an illustration showing a side cross-sectional view of thechannel having the wafer disposed therein, in accordance with oneembodiment of the present invention;

FIG. 4C is an illustration showing a relationship between the immisciblecomponent, the solid component, the contaminant, and the wafer, inaccordance with one embodiment of the present invention;

FIG. 4D is an illustration showing how the immiscible componentfunctions to drive the solid component to within proximity of thecontaminant, in accordance with one embodiment of the present invention;

FIG. 4E is an illustration showing the removal of the contaminant fromthe wafer surface following traversal thereover of the immisciblecomponent, in accordance with one embodiment of the present invention;

FIG. 4F is an illustration showing the removal of the contaminant fromthe wafer surface, in accordance with another embodiment of the presentinvention; and

FIG. 5 is an illustration showing a flowchart of a method for removingcontamination from a substrate, in accordance with another embodiment ofthe present invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Itwill be apparent, however, to one skilled in the art that the presentinvention may be practiced without some or all of these specificdetails. In other instances, well known process operations have not beendescribed in detail in order not to unnecessarily obscure the presentinvention.

FIG. 1 is an illustration showing a physical diagram of a cleaningmaterial 101 for removing contamination 103 from a semiconductor wafer(“wafer”) 105, in accordance with one embodiment of the presentinvention. The cleaning material 101 of the present invention includes acontinuous liquid medium 107, solid components 109, and immisciblecomponents 111. The solid components 109 and immiscible components 111are dispersed within the continuous liquid medium 107. In variousembodiments, the continuous liquid medium 107 can be either aqueous ornon-aqueous. Depending on the particular embodiment, the immisciblecomponents 111 can be defined in either a gas phase, a liquid phase, asolid phase, or a combination of gas, liquid, and solid phases. In oneembodiment, the immiscible components 111 are defined as a mixture ofimmiscible components 111, wherein each immiscible component 111 withinthe mixture has either a common physical state or a different physicalstate. For example, in various embodiments the physical states ofimmiscible components 111 within the mixture of immiscible components111 can include a gas and a liquid, a gas and a solid, a liquid and asolid, or any combination of multiple gases, multiple liquids, andmultiple solids.

It should be appreciated that the immiscible components 111 areimmiscible with respect to the continuous liquid medium 107. In oneexemplary embodiment, the immiscible components 111 are defined as gasbubbles within the continuous liquid medium 107. In another exemplaryembodiment, the immiscible components 111 are defined as liquid dropletswithin the continuous liquid medium 107. Regardless of the particularembodiment associated with the continuous liquid medium 107 andimmiscible components 111, the solid components 109 are dispersed insuspension within the continuous liquid medium 107.

It should be understood that depending on the particular embodiment, thesolid components 109 within the cleaning material 101 may possesphysical properties representing essentially any sub-state within thesolid phase, wherein the solid phase is defined as a phase other thanliquid or gas. For example, physical properties such as elasticity andplasticity can vary among different types of solid components 109 withinthe cleaning material 101. Additionally, it should be understood that invarious embodiments the solid components 109 can be defined ascrystalline solids or non-crystalline solids. Regardless of theirparticular physical properties, the solid components 109 within thecleaning material 101 should be capable of avoiding adherence to thewafer 105 surface when positioned in either close proximity to orcontact with the wafer 105 surface. Additionally, the mechanicalproperties of the solid components 109 should not cause damage to thewafer 105 surface during the cleaning process. Furthermore, the solidcomponents 109 should be capable of establishing an interaction with thecontaminant 103 material present on the wafer 105 surface whenpositioned in either close proximity or contact with the contaminant103. For example, the size and shape of the solid components 109 shouldbe favorable for establishing the interaction between the solidcomponents 109 and the contaminants 103.

The solid components 109 within the cleaning material 101 should becapable of interacting with contaminants 103 on the wafer 105 whileavoiding both adhesion and damage to the wafer 105. Also, the solidcomponents 109 should avoid dissolution in the liquid medium 107 andshould have a surface functionality that enables dispersion throughoutthe liquid medium 107. For solid components 109 that do not have surfacefunctionality that enables dispersion throughout the liquid medium 107,chemical dispersants may be added to the liquid medium 107 to enabledispersion of the solid components 109. Depending on their specificchemical characteristics and their interaction with the surroundingliquid medium 107, the solid components 109 may take one or more ofseveral different forms. For example, in various embodiments the solidcomponents 109 may form aggregates, colloids, gels, coalesced spheres,or essentially any other type of agglutination, coagulation,flocculation, agglomeration, or coalescence. It should be appreciatedthat the exemplary list solid component 109 forms identified above isnot intended to represent an inclusive list. In other embodiments, thesolid components 109 may take a form not specifically identified herein.Therefore, the point to understand is that the solid components 109 canbe defined as essentially any solid material capable of functioning inthe manner previously described with respect to their interaction withthe wafer 105 and the contaminants 103.

Some exemplary solid components 109 include aliphatic acids, carboxylicacids, paraffin, wax, polymers, polystyrene, polypeptides, and othervisco-elastic materials. The solid component 109 material should bepresent at a concentration that exceeds its solubility limit within theliquid medium 107. Also, it should be understood that the cleaningeffectiveness associated with a particular solid component 109 materialmay vary as a function of temperature.

The aliphatic acids represent essentially any acid defined by organiccompounds in which carbon atoms form open chains. A fatty acid is anexample of an aliphatic acid that can be used as the solid components109 within the cleaning material 101. Examples of fatty acids that maybe used as the solid components 109 include capric acid, lauric acid,palmitic acid, myristic acid, stearic acid, oleic acid, arachidic acid,behenic acid, lignoceric acid, and cerotic acid, among others. In oneembodiment, the solid components 109 can represent a mixture of fattyacids defined by various carbon chain lengths extending from C-1 toabout C-26. Carboxylic acids are defined by essentially any organic acidthat includes one or more carboxyl groups (COOH). When used as the solidcomponents 109, the carboxylic acids can include mixtures of variouscarbon chain lengths extending from C-1 through about C-100. Also, thecarboxylic acids can include long-chain alcohols, ethers, and/orketones, above the solubility limit in the liquid medium 107.

In some embodiments, addition of a dispersant material to the liquidmedium 107 may be required to enable a particular type of solidcomponent 109, such as a fatty acid, to disperse throughout the liquidmedium 107. For example, a base can be added to the liquid medium 107 toenable suspension of solid components 109 fowled from materials such ascarboxylic acid or stearic acid that are present in less thanstoichiometric quantities. Additionally, the surface functionality ofthe solid component 109 materials can be influenced by the inclusion ofmoieties that are miscible with the liquid medium 107, such ascarboxylate, phosphate, sulfate groups, polyol groups, ethylene oxide,etc. The point to be understood is that the solid components 109 shouldbe dispersible in a substantially uniform manner throughout the liquidmedium 107 such that the solid components 109 avoid clumping togetherinto a form that cannot be forced to interact with the contaminants 103present on the wafer 105.

As previously mentioned, the continuous liquid medium 107 can be eitheraqueous or non-aqueous. For example, an aqueous liquid medium 107 can bedefined by de-ionized water in one embodiment. In another embodiment, anon-aqueous liquid medium 107 can be defined by a hydrocarbon, afluorocarbon, a mineral oil, or an alcohol, among others. Irrespectiveof whether the liquid medium 107 is aqueous or non-aqueous, it should beunderstood that the liquid medium 107 can be modified to include ionicor non-ionic solvents and other chemical additives. For example, thechemical additives to the liquid medium 107 can include any combinationof co-solvents, pH modifiers, chelating agents, polar solvents,surfactants, ammonia hydroxide, hydrogen peroxide, hydrofluoric acid,tetramethylammonium hydroxide, and rheology modifiers such as polymers,particulates, and polypeptides.

As previously mentioned, the immiscible components 111 within thecleaning material 101 can be defined in either the gas phase, the liquidphase, the solid phase, or a combination thereof. In the embodimenthaving the immiscible components 111 defined in the gas phase, theimmiscible components 111 are defined as gas bubbles dispersedthroughout the continuous liquid medium 107. In one embodiment, the gasbubbles are defined to occupy 5% to 99.9% of the cleaning material 101by volume. In another embodiment, the gas bubbles are defined to occupy50% to 95% of the cleaning material 101 by weight. The gas defining theimmiscible components 111 can be either inert, e.g., N₂, Ar, etc., orreactive, e.g., O₂, O₃, H₂O₂, air, H₂, NH₃, HF, etc.

In the embodiment having the immiscible components 111 defined in theliquid phase, the immiscible components 111 are defined as liquiddroplets dispersed throughout the continuous liquid medium 107, whereinthe liquid droplets are immiscible within the liquid medium 107. Theliquid defining the immiscible components 111 can be either inert orreactive. For example, hexane or mineral oil may be used as an inertliquid for defining the immiscible components 111, wherein the liquidmedium 107 is aqueous. In another example, oil soluble surface modifiersmay be used as a reactive liquid for defining the immiscible components111.

During the cleaning process, a downward force is exerted on the solidcomponents 109 within the liquid medium 107 such that the solidcomponents 109 are brought within close proximity or contact with thecontaminants 103 on the wafer 105. The immiscible components 111 withinthe cleaning material 101 provide the mechanism by which the downwardforce is exerted on the solid components 109. When the solid component109 is forced within sufficient proximity to or contact with thecontaminant 103, an interaction is established between the solidcomponent 109 and the contaminant 103. The interaction between the solidcomponent 109 and the contaminant 103 is sufficient to overcome anadhesive force between the contaminant 103 and the wafer 105. Therefore,when the solid component 109 is moved away from the wafer 105, thecontaminant 103 that interacted with the solid component 109 is alsomoved away from the wafer 105, i.e., the contaminant 103 is cleaned fromthe wafer 105.

FIGS. 2A-2B are illustrations showing how the cleaning material 101functions to remove the contaminant 103 from the wafer 105, inaccordance with one embodiment of the present invention. It should beunderstood that the cleaning material 101 depicted in FIGS. 2A-2Bpossesses the same characteristics as previously described with respectto FIG. 1. As shown in FIG. 2A, within the liquid medium 107 of thecleaning material 101, the solid component 109 is interposed between thecontaminant 103 and the immiscible component 111. The immisciblecomponent 111 within the liquid medium, whether gas bubbles or liquiddroplets, has an associated surface tension. Therefore, when theimmiscible component 111 is pressed downward against the solid component109, the immiscible component 111 becomes deformed and exerts a downwardforce (F) on the solid component 109. This downward force (F) serves tomove the solid component 109 toward the wafer 105 and contaminant 103thereon. In one embodiment, the interaction between the solid component109 and contaminant 103 occurs when the solid component 109 is forcedsufficiently close to the contaminant 103. In another embodiment, theinteraction between the solid component 109 and contaminant 103 occurswhen the solid component 109 actually contacts the contaminant 103.

The interaction force between the solid component 109 and thecontaminant 103 is stronger than the force connecting the contaminant103 to the wafer 105. Additionally, in an embodiment where the solidcomponent 109 binds with the contaminant 103, a force used to move thesolid component 109 away from the wafer 105 is stronger than the forceconnecting the contaminant 103 to the wafer 105. Therefore, as depictedin FIG. 2B, when the solid component 109 is moved away from the wafer105, the contaminant 103 bound to the solid component 109 is also movedaway from the wafer 105. It should be appreciated that because the solidcomponents 109 interact with the contamination 103 to affect thecleaning process, contamination 103 removal across the wafer 105 will bedependent on how well the solid components 109 are distributed acrossthe wafer 105. In a preferred embodiment, the solid components 109 willbe so well distributed that essentially every contaminant 103 on thewafer 105 will be in proximity to at least one solid component 109. Itshould also be appreciated that one solid component 109 may come incontact with or interact with more than one contaminant 103, either in asimultaneous manner or in a sequential manner.

Interaction between the solid component 109 and the contaminant 103 canbe established through one or more mechanisms including adhesion,collision, and attractive forces, among others. Adhesion between thesolid component 109 and contaminant 103 can be established throughchemical interaction and/or physical interaction. For example, in oneembodiment, chemical interaction causes a glue-like effect to occurbetween the solid component 109 and the contaminant 103. In anotherembodiment, physical interaction between the solid component 109 and thecontaminant 103 is facilitated by the mechanical properties of the solidcomponent 109. For example, the solid component 109 can be malleablesuch that when pressed against the contaminant 103, the contaminant 103becomes imprinted within the malleable solid component 109. In anotherembodiment, the contaminant 103 can become entangled in a network ofsolid components 109. In this embodiment, mechanical stresses can betransferred through the network of solid components 109 to thecontaminant 103, thus providing the mechanical force necessary forremoval of the contaminant 103 from the wafer 105.

Deformation of the solid component 109 due to imprinting by thecontaminant 103 creates a mechanical linkage between the solid component109 and the contaminant 103. For example, a surface topography of thecontaminant 103 may be such that as the contaminant 103 is pressed intothe solid component 109, portions of the solid component 109 materialenters regions within the surface topography of the contaminant 103 fromwhich the solid component 109 material cannot easily escape, therebycreating a locking mechanism. Additionally, as the contaminant 103 ispressed into the solid component 109, a vacuum force can be establishedto resist removal of the contaminant 103 from the solid component 109.

In another embodiment, energy transferred from the solid component 109to the contaminant 103 through direct or indirect contact may cause thecontaminant 103 to be dislodged from the wafer 105. In this embodiment,the solid component 109 may be softer or harder than the contaminant103. If the solid component 109 is softer than the contaminant 103,greater deformation of the solid component 109 is likely to occur duringthe collision, resulting in less transfer of kinetic energy fordislodging the contaminant 103 from the wafer 105. However, in the casewhere the solid component 109 is softer than the contaminant 103, theadhesive connection between the solid component 109 and the contaminant103 may be stronger. Conversely, if the solid component 109 is at leastas hard as the contaminant 103, a substantially complete transfer ofenergy can occur between the solid component 109 and the contaminant103, thus increasing the force that serves to dislodge the contaminant103 from the wafer 105. However, in the case where the solid component109 is at least as hard as the contaminant 103, interaction forces thatrely on deformation of the solid component 109 may be reduced. It shouldbe appreciated that physical properties and relative velocitiesassociated with the solid component 109 and the contaminant 103 willinfluence the collision interaction therebetween.

In addition to the foregoing, in one embodiment, interaction between thesolid component 109 and contaminant 103 can result from electrostaticattraction. For example, if the solid component 109 and the contaminant103 have opposite surface charges they will be electrically attracted toeach other. It is possible that the electrostatic attraction between thesolid component 109 and the contaminant 103 can be sufficient toovercome the force connecting the contaminant 103 to the wafer 105.

In another embodiment, an electrostatic repulsion may exist between thesolid component 109 and the contaminant 103. For example, both the solidcomponent 109 and the contaminant 103 can have either a negative surfacecharge or a positive surface charge. If the solid component 109 and thecontaminant 103 can be brought into close enough proximity, theelectrostatic repulsion therebetween can be overcome through van derWaals attraction. The force applied by the immiscible component 111 tothe solid component 109 may be sufficient to overcome the electrostaticrepulsion such that van der Waals attractive forces are establishedbetween the solid component 109 and the contaminant 103. Additionally,in another embodiment, the pH of the liquid medium 107 can be adjustedto compensate for surface charges present on one or both of the solidcomponent 109 and contaminant 103, such that the electrostatic repulsiontherebetween is reduced to facilitate interaction.

FIG. 3 is an illustration showing a flowchart of a method for removingcontamination from a substrate, in accordance with one embodiment of thepresent invention. It should be understood that the substrate referencedin the method of FIG. 3 can represent a semiconductor wafer or any othertype of substrate from which contaminants associated with asemiconductor fabrication process need to be removed. Also, thecontaminants referenced in the method of FIG. 3 can representessentially any type of contaminant associated with the semiconductorwafer fabrication process, including but not limited to particulatecontamination, trace metal contamination, organic contamination,photoresist debris, contamination from wafer handling equipment, andwafer backside particulate contamination.

The method of FIG. 3 includes an operation 301 for disposing a cleaningmaterial over a substrate, wherein the cleaning material includes solidcomponents dispersed within a liquid medium. The cleaning materialreferenced in the method of FIG. 3 is the same as previously describedwith respect to FIGS. 1, 2A, and 2B. Therefore, the solid componentswithin the cleaning material are dispersed in suspension within theliquid medium. Also, the solid components are defined to avoid damagingthe substrate and to avoid adherence to the substrate. In oneembodiment, the solid components are defined as crystalline solids. Inanother embodiment, the solid components are defined as non-crystallinesolids. In yet another embodiment, the solid components are representedas a combination of crystalline and non-crystalline solids.Additionally, in various embodiments, the liquid medium can be eitheraqueous or non-aqueous.

The method also includes an operation 303 for applying a force to asolid component to bring the solid component within proximity to acontaminant present on the substrate, such that an interaction isestablished between the solid component and the contaminant. Aspreviously discussed, immiscible components are provided within thecleaning material to apply the force to the solid component necessary tobring the solid component within proximity to the contaminant. In oneembodiment, the method can include an operation for controlling theimmiscible components to apply a controlled amount of force to the solidcomponent. The immiscible components can be defined as gas bubbles orimmiscible liquid droplets within the liquid medium. Additionally, theimmiscible components can be represented as a combination of gas bubblesand immiscible liquid droplets within the liquid medium.

In one embodiment of the method, the immiscible components are definedwithin the liquid medium prior to disposing the cleaning material overthe substrate. However, in another embodiment, the method can include anoperation to form the immiscible components in-situ followingdisposition of the cleaning material over the substrate. For example,the immiscible components can be formed from a dissolved gas within theliquid medium upon a decrease in ambient pressure relative to thecleaning material. It should be appreciated that formation of theimmiscible components in situ may enhance the contamination removalprocess. For example, in one embodiment, gravity serves to pull thesolid components toward the substrate prior to formation of theimmiscible components. Then, the ambient pressure is reduced such thatgas previously dissolved within the liquid medium comes out of solutionto form gas bubbles. Because the solid components have been pulled bygravity toward the substrate, the majority of gas bubbles will formabove the solid components. Formation of the gas bubbles above the solidcomponents, with the solid components already settled toward thesubstrate, will serve to enhance movement of the solid components towithin proximity of the contaminants on the substrate.

In various embodiments, the interaction between the solid component andthe contaminant can be established by adhesive forces, collision forces,attractive forces, or a combination thereof. Also, in one embodiment,the method can include an operation for modifying a chemistry of theliquid medium to enhance interaction between the solid component and thecontaminant. For example, the pH of the liquid medium can be modified tocancel surface charges on one or both of the solid component andcontaminant such that electrostatic repulsion is reduced.

Additionally, in one embodiment, the method can include an operation forcontrolling a temperature of the cleaning material to enhanceinteraction between the solid component and the contaminant. Morespecifically, the temperature of the cleaning material can be controlledto control the properties of the solid component. For example, at ahigher temperature the solid component may be more malleable such thatit conforms better when pressed against the contaminant. Then, once thesolid component is pressed and conformed to the contaminant, thetemperature is lowered to make the solid component less malleable tobetter hold its conformal shape relative to the contaminant, thuseffectively locking the solid component and contaminant together. Thetemperature may also be used to control the solubility and therefore theconcentration of the solid components. For example, at highertemperatures the solid component may be more likely to dissolve in theliquid medium. The temperature may also be used to control and/or enableformation of solid components in-situ on the wafer from liquid-liquidsuspension.

In a separate embodiment, the method can include an operation forprecipitating solids dissolved within the continuous liquid medium. Thisprecipitation operation can be accomplished by dissolving the solidsinto a solvent and then adding a component that is miscible with thesolvent but that is immiscible with the solid. Addition of the componentthat is miscible with the solvent but that is immiscible with the solidcauses the precipitation of a solid component.

The method further includes an operation 305 for moving the solidcomponent away from the substrate such that the contaminant thatinteracted with the solid component is removed from the substrate. Inone embodiment, the method includes an operation for controlling a flowrate of the cleaning material over the substrate to control or enhancemovement of the solid component and/or contaminant away from thesubstrate.

The method of the present invention for removing contamination from asubstrate can be implemented in many different ways so long as there isa means for applying a force to the solid components of the cleaningmaterial such that the solid components establish an interaction withthe contaminants to be removed. FIG. 4A is an illustration showing anapparatus for removing contamination from a wafer, in accordance withone embodiment of the present invention. The apparatus includes achannel 401 for receiving the wafer 105, as indicated by arrow 403. Itshould be appreciated that the length 402 and height 404 of the channel401 interior is defined to accommodate the wafer 105. Also, in oneembodiment the height 404 of the channel 401 is adjustable. The channel401 is defined to contain the cleaning material 101, as previouslydescribed. Thus, when the wafer 105 is moved into the channel 401, thewafer 105 is submerged within the cleaning material 101. It should beappreciated that the channel 401 can be made from any material ofsufficient strength that is chemically compatible with the cleaningmaterial 101 and wafer 105.

FIG. 4B is an illustration showing a side cross-sectional view of thechannel 401 having the wafer 105 disposed therein, in accordance withone embodiment of the present invention. The channel 401 includes aconstraining surface 406 positioned in an opposing and substantiallyparallel orientation with respect to the surface of the wafer 105 fromwhich contamination is to be removed. The channel 401 and wafer 105 aretilted at an angle 412 with respective to a horizontal plane 408. At alower end/elevation of the channel 401, an immiscible componentgenerator 409 is provided for generating immiscible components 111within the liquid medium 107.

As previously discussed, the immiscible components 111 can be formedfrom either gas or liquid that is immiscible within the liquid medium107. The immiscible component 111 material is provided from a source 405through a line 407 to the immiscible component generator 409. During thecleaning operation, a motive force is applied to move the immisciblecomponents 111 over the wafer 105 with a velocity V. It should beappreciated that as the immiscible components 111 are moved over thewafer 105, the position of the immiscible components relative to thewafer 105 is constrained by the constraining surface 406 of the channel401. In one embodiment, the motive force applied to move the immisciblecomponents 111 over the wafer 105 is a buoyant force. In anotherembodiment, a dispensing pressure of the immiscible component generator409 provides the motive force for moving the immiscible components 111over the wafer 105.

In various embodiments, the immiscible component generator 409 can beconfigured to have either a single generation point or multiplegeneration points. For example, in one embodiment, the immisciblecomponent generator 409 is defined as a manifold configured to include anumber of immiscible component 111 generation points. Additionally, itshould be appreciated that the apparatus can include a substrate holderdefined to rotate and/or translate the wafer 105 within the channelduring the cleaning process.

FIG. 4C is an illustration showing a relationship between the immisciblecomponent 111, the solid component 109, the contaminant 103, and thewafer 105. As the immiscible component 111 moves over the wafer 105surface, a thickness 410 of cleaning material separates the immisciblecomponent-to-liquid medium interface from the wafer 105 surface. Itshould be appreciated that in the embodiment where buoyant force drivesthe movement of the immiscible components 111 over the wafer 105, anincrease in tilt angle 412 will cause a corresponding increase in thebuoyant force. As the buoyant force and corresponding velocity V of theimmiscible component 111 increases, the immiscible component 111 canbecome elongated, thus increasing the cleaning material thickness 410.If the thickness 410 of the cleaning material becomes sufficientlylarge, the immiscible component 111 may not be capable of exerting asufficient force on the solid component 109 to enable interaction withthe contaminant 103. Also, as the immiscible component 111 velocity Vincreases, the residency time of the immiscible component 111 at a givenlocation over the wafer 105 surface decreases. Therefore, the tilt angle412 should be set to appropriately control the immiscible component 111velocity V. Also, the separation distance 404 between the constrainingsurface 406 and the wafer 105 should be controlled such that thecleaning material thickness 410 does not become too large.

FIG. 4D is an illustration showing how the immiscible component 111functions to drive the solid component 109 to within proximity of thecontaminant 103, in accordance with one embodiment of the presentinvention. As the immiscible component 111 traverses over the solidcomponent 109 and contaminant 103 within the liquid medium 107, theimmiscible component forces the solid component 109 toward thecontaminant 103 with a force F. As previously discussed, interactionoccurs between the solid component 109 and contaminant 103 when they areforced within sufficient proximity to each other. The force F exerted bythe immiscible component 111 on the solid component 109 is related to apressure differential between the immiscible component 111 and theliquid medium 107. Additionally, the contaminant 103 is further exposedto shear stresses within the cleaning material thickness 410. Also, thecontaminant 103 is exposed to interfacial forces present at the boundarybetween the immiscible component 111 and the liquid medium 107. Theseshear stresses and interfacial forces serve to assist in dislodging thecontaminant 103 from the wafer 105 surface.

FIG. 4E is an illustration showing the removal of the contaminant 103from the wafer 105 surface following traversal thereover of theimmiscible component 111, in accordance with one embodiment of thepresent invention. In the embodiment of FIG. 4E, the solid component 109and contaminant 103 are removed from the wafer 105 as a combined unitunder the influence of shear stresses and interfacial forces aspreviously discussed. In another embodiment, the solid component 109interacts with the contaminant 103 to remove the contaminant 103 fromthe wafer 105 without actually combining with the contaminant 103. Inthis embodiment, each of the solid component 109 and the contaminant 103will individually move away from the wafer 105. In one embodiment,removal of the contaminant 103 from the wafer 105 can be enhanced byshear forces associated with a flow of the cleaning material through thechannel 401. In this embodiment, the apparatus can include a cleaningmaterial circulator defined to induce a flow within the cleaningmaterial such that contaminants 103 having interacted with the solidcomponents 109 are moved away from the wafer 105.

FIG. 4F is an illustration showing the removal of the contaminant 103from the wafer 105 surface, in accordance with another embodiment of thepresent invention. In embodiment of FIG. 4F, the liquid medium 107 isaqueous, the immiscible component 111 is non-aqueous, and the solidcomponent 109 is surface active. As the immiscible component 111traverses over the solid component 109, the immiscible component notonly exerts force F on the solid component 109, but also wets the solidcomponent 109, such that the solid component 109 is pulled into theinterface region between the immiscible component 111 and the liquidmedium 107. Thus, removal of the solid component 109 and contaminant 103combination from the wafer 105 is enhanced by the adsorption of thesolid component 109 to the immiscible-liquids interface.

Although the apparatus of FIGS. 4A-4F has been described with respect toparticular exemplary embodiments, it should be appreciated that theprinciples for removing contaminants from the wafer can be equallyapplied in other embodiments of the apparatus. For example, theapparatus of FIGS. 4A-4F can be modified to maintain the wafer in ahorizontal, vertical, or upside-down orientation so long as a motiveforce for the immiscible components 111 is provided such that theimmiscible components 111 exert the force F on the solid components 109to enable their interaction with the contaminants 103. Also, in variousembodiments, the wafer 105 may be spun, pulled, pushed, or otherwiseagitated in conjunction with traversal of the immiscible components 111over the wafer 105.

Additionally, the cleaning process performed using the apparatus ofFIGS. 4A-4F in conjunction with the method of FIG. 3 can be performed inaccordance with recipes that prescribe particular control settings forparameters such as temperature, pressure, flow rates, and time. In oneembodiment, the apparatus can include a cleaning material control systemdefined to monitor and adjust a chemistry of the cleaning material toenhance interaction between the solid components 109 and thecontaminants 103 and enhance removal of the contaminants 103 from thewafer 105. Also, in one embodiment, the apparatus can include atemperature control system defined to control the temperature of thecleaning material within the channel 401. Furthermore, the cleaningprocess performed using the apparatus of FIGS. 4A-4F in conjunction withthe method of FIG. 3 can be performed in an iterative manner, i.e.,multiple step manner. Also, the principles described with respect to thesingle wafer 105 apparatus of FIGS. 4A-4F can be extended to anapparatus configured to process multiple wafers 105 in a simultaneousmanner.

FIG. 5 is an illustration showing a flowchart of a method for removingcontamination from a substrate, in accordance with another embodiment ofthe present invention. The method includes an operation 501 forsubmerging a substrate in a cleaning material such that a surface of thesubstrate from which contamination is to be removed is positioned in anopposing and substantially parallel orientation with respect to aconstraining surface. FIGS. 4A-4F, as previously discussed, illustratean example of the substrate being positioned in the opposing andsubstantially parallel orientation with respect to the constrainingsurface, while being submerged within the cleaning material. It shouldbe appreciated that the cleaning material referenced in the method ofFIG. 5 represents the same cleaning material 101, as previouslydescribed. Therefore, the cleaning material includes solid components109 dispersed within a liquid medium 107.

The method also includes an operation 503 for tilting the substratetogether with the constraining surface, relative to a horizontal plane.In various embodiments, the tilting can be performed either before orafter positioning of the substrate in the opposing and substantiallyparallel orientation with the constraining surface. The method furtherincludes an operation 505 for generating immiscible components withinthe cleaning material at a location corresponding to an elevation lowerthan the substrate. FIG. 4B, as previously discussed, illustrates anexample of the immiscible components 111 being generated within thecleaning material at an elevation lower than that of the substrate,wherein the wafer 105 represents the substrate.

A buoyant force acting upon the immiscible components causes theimmiscible components to move over substrate, between the constrainingsurface and the substrate. Movement of the immiscible components overthe substrate causes a force to be applied to the solid componentswithin the liquid medium such that the solid components interact withcontaminants present on the substrate. FIGS. 4C-4F, as previouslydiscussed, illustrate an example of how the immiscible components exertforce on the solid components to facilitate interaction between thesolid components and the contaminants such that the contaminants areremoved from the substrate.

The method as described in the flowchart of FIG. 5 can include a numberof additional operations to enhance the contamination removal process.In one embodiment, an operation can be included for adjusting an angleof tilt of the substrate together with the constraining surface toenable control of the immiscible component velocity over the substrate.Also, an operation can be included for adjusting a separation distancebetween the constraining surface and the substrate to enable control ofa distance between the immiscible components and the substrate, as theimmiscible components move over the substrate.

In another operation, the cleaning material can be circulated to inducea flow of cleaning material over the substrate. It should be appreciatedthat inducing a flow of cleaning material over the substrate can allowfor replenishment of chemical species within the cleaning material andenhance movement of removed contaminants away from the substrate. Themethod can further include an operation for monitoring and adjusting thecleaning material chemistry to enhance interaction between the solidcomponents and the contaminants, thus enhancing removal of thecontaminants from the substrate. Additionally, the temperature of thecleaning material can be monitored and adjusted to enhance interactionbetween the solid components and the contaminants. It should also beappreciated that an operation can be performed to manipulate thesubstrate through either rotation, translation, or both rotation andtranslation, as the immiscible components move over the substrate.

Although the present invention has been described in the context ofremoving contaminants from a semiconductor wafer, it should beunderstood that the previously described principles and techniques ofthe present invention can be equally applied to cleaning surfaces otherthan semiconductor wafers. For example, the present invention can beused to clean any equipment surface used in semiconductor manufacturing,wherein any equipment surface refers to any surface that is inenvironmental communication with the wafer, e.g., shares air space withthe wafer. The present invention can also be used in other technologyareas where contamination removal is important. For example, the presentinvention can be used to remove contamination on parts used in the spaceprogram, or other high technology areas such as surface science, energy,optics, microelectronics, MEMS, flat-panel processing, solar cells,memory devices, etc. It should be understood that the aforementionedlisting of exemplary areas where the present invention may be used isnot intended to represent an inclusive listing. Furthermore, it shouldbe appreciated that the wafer as used in the exemplary descriptionherein can be generalized to represent essentially any other structure,such as a substrate, a part, a panel, etc.

While this invention has been described in terms of several embodiments,it will be appreciated that those skilled in the art upon reading thepreceding specifications and studying the drawings will realize variousalterations, additions, permutations and equivalents thereof. Therefore,it is intended that the present invention includes all such alterations,additions, permutations, and equivalents as fall within the true spiritand scope of the invention.

1. An apparatus for removing contamination from a substrate, comprising:a channel for receiving a substrate, the channel being defined toinclude a constraining surface positioned in an opposing andsubstantially parallel orientation with respect to a surface of thesubstrate from which contamination is to be removed; a cleaning materialdisposed within the channel such that the substrate to be received bythe channel is submerged within the cleaning material, the cleaningmaterial defined as a liquid medium including dispersed solidcomponents; and an immiscible component generator disposed within thechannel to generate immiscible components within the cleaning materialsuch that a motive force is applied to move the immiscible componentsbetween the constraining surface of the channel and the surface of thesubstrate from which contamination is to be removed.
 2. An apparatus forremoving contamination from a substrate as recited in claim 1, whereinthe immiscible components apply a force to the solid components withinthe liquid medium to bring the solid components within proximity tocontaminants present on the substrate such that an interaction isestablished between the solid components and the contaminants.
 3. Anapparatus for removing contamination from a substrate as recited inclaim 1, wherein movement of the immiscible components between theconstraining surface of the channel and the surface of the substratecauses the solid components that have interacted with contaminants to bemoved away from the substrate such that the contaminants are removedfrom the substrate.
 4. An apparatus for removing contamination from asubstrate as recited in claim 1, further comprising: a cleaning materialcirculator defined to induce a flow within the cleaning material suchthat solid components having interacted with contaminants are moved awayfrom the substrate.
 5. An apparatus for removing contamination from asubstrate as recited in claim 1, wherein the channel is defined to bepositioned at an angle with respect to horizontal such that the motiveforce for moving the immiscible components is a buoyant force.
 6. Anapparatus for removing contamination from a substrate as recited inclaim 1, wherein the channel is defined to enable adjustment of aseparation distance between the constraining surface of the channel andthe surface of the substrate.
 7. An apparatus for removing contaminationfrom a substrate as recited in claim 1, further comprising: a cleaningmaterial control system defined to monitor and adjust a chemistry of thecleaning material to enhance interaction between the solid componentsand the contaminants and enhance removal of the contaminants from thesubstrate.
 8. An apparatus for removing contamination from a substrateas recited in claim 1, further comprising: a temperature control systemdefined to control a temperature of the cleaning material within thechannel.
 9. An apparatus for removing contamination from a substrate asrecited in claim 1, wherein the immiscible component generator isdefined to generate immiscible components in either a liquid phase or agas phase.
 10. An apparatus for removing contamination from a substrateas recited in claim 1, wherein the immiscible component generator isdefined as a manifold for generating a number of immiscible componenttrains across the surface of the substrate.
 11. An apparatus forremoving contamination from a substrate as recited in claim 1, furthercomprising: a substrate holder defined to either rotate, translate, orboth rotate and translate the substrate within the channel.
 12. Anapparatus for removing contamination from a substrate as recited inclaim 1, wherein the apparatus is defined to remove contamination frommultiple substrates in a simultaneous manner.
 13. A method for removingcontamination from a substrate, comprising: submerging a substrate in acleaning material such that a surface of the substrate from whichcontamination is to be removed is positioned in an opposing andsubstantially parallel orientation with respect to a constrainingsurface, the cleaning material including solid components dispersedwithin a liquid medium; tilting the substrate together with theconstraining surface relative to a horizontal plane; and generatingimmiscible components within the cleaning material at a locationcorresponding to an elevation lower than the substrate such that abuoyant force acting upon the immiscible components causes theimmiscible components to move over substrate between the constrainingsurface and the substrate, movement of the immiscible components overthe substrate causing a force to be applied to the solid componentswithin the liquid medium such that the solid components interact withcontaminants present on the substrate.
 14. A method for removingcontamination from a substrate as recited in claim 13, wherein the solidcomponents form a network of solid components within the liquid medium,wherein mechanical stress transferred through the network of solidcomponents interact with the contaminants.
 15. A method for removingcontamination from a substrate as recited in claim 13, wherein theimmiscible components are defined as gas bubbles within the liquidmedium.
 16. A method for removing contamination from a substrate asrecited in claim 13, wherein the immiscible components are defined asliquid droplets within the liquid medium.
 17. A method for removingcontamination from a substrate as recited in claim 13, furthercomprising: adjusting an angle of tilt of the substrate together withthe constraining surface to control a velocity of the immisciblecomponents over the substrate.
 18. A method for removing contaminationfrom a substrate as recited in claim 13, further comprising: adjusting aseparation distance between the constraining surface and the substrateto control a distance between the immiscible components and thesubstrate as the immiscible components move over the substrate.
 19. Amethod for removing contamination from a substrate as recited in claim13, further comprising: circulating the cleaning material to induce aflow of cleaning material over the substrate.
 20. A method for removingcontamination from a substrate as recited in claim 13, furthercomprising: manipulating the substrate through either rotation,translation, or both rotation and translation as the immisciblecomponents move over the substrate.